Adaptive Processing for Images Captured with Flash

1. A computer-implemented process for improving images taken with flash, comprising using a computer to perform the process actions of: (a) acquiring a first image captured with flash and ambient light; (b) acquiring a second image, corresponding to the first image, captured with ambient light; (c) using the first image and the second image to create a third flash-only image; (d) estimating the ambient light color from the second image taken with ambient light only; (e) white-balancing the second image using the estimated ambient light color to obtain a white-balanced ambient light image; (f) white-balancing the third flash-only image to a known flash color to create a white-balanced flash-only image; (g) adding the white-balanced ambient light image and the white-balanced flash only image to obtain an image white-balanced for flash and ambient light; (h) obtaining additional white-balanced flash-only images; and (i) adding the additional white-balanced flash-only images to the white-balanced ambient light image to obtain multiple images white-balanced for flash and ambient light.

2. The computer-implemented process of claim 1 wherein the flash-only image is created by subtracting the second image from the corresponding first image to obtain the third flash-only image.

3. The computer-implemented process of claim 1 wherein the first and second images are acquired by selecting them from a plurality of images taken of the same subject matter.

4. The computer-implemented process of claim 1 further comprising the process actions of: reducing hot spots in the image white-balanced for flash and ambient light.

5. The computer-implemented process of claim 1 further comprising the process actions of: after white-balancing the third flash-only image to a known flash color to create a white-balanced flash only image, white-balancing the flash only image again for a specified color, before adding the white-balanced ambient light image and the white-balanced flash only image to obtain an image white-balanced for flash and ambient light wherein foreground objects reflect the specified color.

6. The computer-implemented process of claim 1 wherein the ambient light is very little, and wherein the ambient light image is taken with a long exposure, and wherein the flash-only image is obtained by assuming the ambient light is approximately zero.

7. A computer-implemented process for improving images taken with flash, comprising using a computer to perform the process actions of: (a) acquiring a first image captured with flash and ambient light; (b) acquiring a second image, corresponding to the first image, captured with ambient light; (c) using the first image and the second image to create a third flash-only image; (d) estimating the ambient light color from the second image taken with ambient light only; (e) white-balancing the second image using the estimated ambient light color to obtain a white-balanced ambient light image; (f) white-balancing the third flash-only image to a known flash color to create a white-balanced flash-only image; (g) adding the white-balanced ambient light image and the white-balanced flash only image to obtain an image white-balanced for flash and ambient light; (h) reducing hot spots in the image white-balanced for flash and ambient light comprising the actions of: converting the image white-balanced for flash and ambient light into the frequency domain; converting the white-balanced ambient light image into the frequency domain; converting the flash-only image into the frequency domain; finding a hot spot in the flash-only image converted into the frequency domain; for any hot spot found in the flash-only image converted into the frequency domain, designating its location as the location of the mid-frequency band of the image white-balanced for flash and ambient light converted into the frequency domain, and the location of the mid-frequency band of the ambient light image converted into the frequency band; and replacing the mid-frequency band of the image white-balanced for flash and ambient light converted into the frequency domain with the mid-frequency of white-balanced ambient light image converted into the frequency domain.

8. The computer-implemented process of claim 7 wherein hot spots are on faces, and wherein face detection is used in finding the hot spots.

9. The computer-implemented process of claim 8 , wherein the face detection used in finding the hot spots is automatic.

10. The computer-implemented process of claim 9 wherein the face detection used in finding the hot spots is manually performed by a user that identifies the location of a face.

11. The computer-implemented process of claim 7 wherein the process action of finding a hot spot comprises using a band-pass filter or bilateral filter.

12. A system for improving the appearance of an image taken with flash, comprising: a general purpose computing device; a computer program comprising program modules executable by the general purpose computing device, wherein the computing device is directed by the program modules of the computer program to, acquire a first image illuminated by ambient lighting; acquire a second image corresponding to the first image, the second image illuminated by a known light source in addition to the ambient lighting; white-balance the second image for a color associated with the known light source; white-balance the second image for a specified color to create a third image white-balanced for a specified color; white-balance the first image for a color associated with the ambient light; and combine the first and third white-balanced images to form a processed image.

13. The system of claim 12 wherein the computing device is embodied in one of: a desk top personal computer; a notebook computer; a camera; a cellular phone; a video camera.

14. The system of claim 12 wherein the ambient lighting is very little, and wherein the first image is taken with a long exposure.

15. The system of claim 12 further comprising a module for adjusting the flash strength in the processed image.

16. A method for correcting images taken with flash, comprising: (a) acquiring a first image captured with flash and ambient light; (b) acquiring a second image, corresponding to the first image, captured with ambient light only; (c) interpolating between the first and second images to achieve images representing various gradations of flash; (d) selecting an image with the preferred gradation of flash; (e) white-balancing the selected image by: (1) using the second image and the selected image to obtain a third flash-only image; (2) estimating an ambient light color from the second image taken with ambient light only; (3) white-balancing the second image using the estimated ambient light color to obtain a white-balanced ambient light image; (4) white-balancing the flash-only image for a known flash color to create a white-balanced flash only image; (5) white-balancing the white-balanced flash-only image for a desired color-tone to create a color-toned white-balanced flash only image; and (6) adding the color-toned white-balanced flash only image and the white-balanced ambient light image to obtain the selected image that is white-balanced for the preferred flash gradation, color tone, and ambient light.

17. The method of claim 16 wherein the ambient light is very little, and wherein the ambient light image is taken with a long exposure, and wherein the flash-only image is obtained by assuming the ambient light is approximately zero.

18. The method of claim 16 further comprising extrapolating from the first and second images to achieve images representing various gradations of flash.